I came across what seems to be a limit in the number of evolutions I can use in both Turbulent and Fractal Noise. I was following a recipe for simulating dirt on old film stock - you create a solid layer add one of the noise FXs then change the contrast up to 350 and brightness down to -90 or so, use the Silhouette Luma transfer mode and hey presto instant dirt!
The clip I am "dirtying" is 1 minute, 8 seconds and 23 frames long. So a quick calculation for 25fps (I'm using PAL footage) and I get 1723 frames! My logic was that since the dirt needs to jump around on each frame if I set the number of evolutions to 1723 I'd get very jumpy dirt, which is what I want - dirt jumps randomly frame to frame and not move across or appear in exactly the same spot on different frames.
It works but only for the first few seconds and then, with both Turbulent and Fractal Noise it stops evolving! Is there a limit here? I can't see anything in the manual and nothing turned up when I Googled or searched through the forums.
I'm running AE CS4 9.0.2 under Windows XP sp3 with 4GB RAM with the 3gig switch on.
My work around was to use several keyframes throughout the clip every 2 seconds with keyframes for evolution set to 0 then 50, then 0 again and 50 again then back to 0 again...etc. This worked a treat. But am I missing something obvious about how these useful and versatile FX work?
The recipie for the old footage BTW was here:
I made my own vignette, a custom flattened curve to reduce contrast. I added an adjustment layer for brightness with a wiggle, another with a wiggled blur as well scaling up the footage 105%, added noise and used a slight jumpy wiggle on the position. Then I threw on the dirt and slowed down the footage to 16fps. But the scratches didn't work for me and it looks convincing without.
Cheers for the response. I was looking around at some your projects; you are deviously deep and beautifully creative when it comes to manipulating pixels in After Effects. I like your RGB screen look!